Method of making folds in coated fiber containers

ABSTRACT

A method of making folds in containers formed from a laminate comprised of a paper or fiberboard body layer having an impervious layer or coating affixed to a surface thereof which forms the interior of the container, the container is erected having folds therein which are formed by folding the laminate at fold lines such that only the coated surface is exposed at the extremity of the folds. The present method comprises initially inversely pre-folding the laminate at the fold lines and then performing the principle folding operation whereby the surface fibers in the fiber layer are prevented from puncturing the coating layer at the folds during the principle folding operation.

United States Patent Deuel Dec. 3, 1974 METHOD OF MAKING FOLDS 1N COATED 3,329,555 7/1967 Sonncborn et al 161/104 3,374,715 3/1968 Koning 117/44 X FIBER CONTAINERS 3,540,490 l1/l970 Jensen et al. 229/45 UX Inventor: James Leslie Deuel, g Grove, 3,603,219 9/1971 Hallis 93/36 PC x Am C C an [73] Asslgnee 22522 g r y, Primary Examiner-Charles E. Van Horn A i n firqm n reDe d,Afimnonsnw V. Filed! 1972 Attorney, Agent, or Firm-Robert P. Auber;Joseph [211 App]. NO: 305,727 J. Orlando; George P. Ziehmer 7] 7 ABSTRACT [52] US. Cl 156/227, 93/36 PC, 93/53 BF, A method of making folds in containers formed from 117/8, 161/117, 229/31 a laminate comprised of a paper or fiberboard body [51] Int. Cl B3lf 1/00 layer having an impervious layer or coating affixed to [58] Field of Search 156/226, 227, 211, 228, a surface thereof which forms the interior of the con- 156/204, 250, 257, 268; 117/2, 4, 8, 10, 44; tainer, the container is erected having folds therein 93/36 PC, 58 ST, 53 BF; 161/117, 104; which are formed by folding the laminate at fold lines 229/31, 3.5, 4.5, 344 such that only the coated surface is exposed at the extremity of the folds. The present method comprises [561 i1:32:2151121255535311,ziirizrgiasnzg zpiiif UNITED STATES PATENTS tion whereby the surface fibers in the fiber layer are 2,949,827 8/1960 Kampen et a1. 93/58 ST prevented f puncturing h coating layer at the 3,058,868 10/1962 Schroeder 156/211 X folds during the principle folding Operation 3,085,026 4/1963 Weisgerber et al. 93/58 ST X 11/1964 Rumberger 117/2 R X 4 Claims, 4 Drawing Figures METHOD OF MAKING FOLDS IN COATED FIBER CONTAINERS I The present invention relates generally to the formation of folds in coated fiber containers. More particularly, the present invention relates to an improved method of making folds in coated fiber containers whereby the integrity of the extremities of the folds are substantially improved.

In the production of coated fiber containers adapted for holding liquid substances and wherein the coated surface forms the interior of the container, it is necessary that some folds be formed in the interior of the containers during the erection thereof. These folds, which are generally the result of the production of corners and seams in the containers, are formed so that the coated surface only is exposed at the extremity of the folds. The purpose of thus forming the folds on the interior of the containers is so that the exposed fiber portions of the marginal edges of the coated fiber board, which would be subjected to a wicking action if exposed to the liquid contents, are protected and not permitted to come into contact with the liquid contents. Examples of such methods of folding coated fiberboard containers can be found in U.S. Pat. No. 3,058,868, to Schroeder, granted Oct. 16, 1962, and U.S. Pat. No. 3,540,490, to Jensen et al., granted Nov. 17, 1970. Each of these patents is concerned with providing a seam in a coated fiber container, a portion of which is located on the interior thereof, wherein one of the overlapping marginal edge portions of the laminate is folded to thereby expose only the coated surface at the extremity of the fold. However, it has been found that unless the impervious layer or coating is provided with a sufficient strength and thickness, wicking at the interior folds of the coated fiber container still occurs. This is due to the existence of numerous minute punctures at the extremity of the folds caused by brittle fibers at or near the surface of the paper or fiberboard material which do no break or bend during the folding operation and hence are apt to penetrate the surface coating. This penetration of the coating layer results in the punctures mentioned and may occasionally also be responsible for splitting of the coating layer along the fold line. The brittleness of the fibers at the surface of the paper or fiberboard layer results from penetration thereof by the coating material which is applied to the fiber layer in a molten form and which penetrates the surface and adheres to the surface fibers thus causing the surface fibers to be cohesively bonded together. Thus, these surface fibers are not free to bend, being extremely stiff and brittle as the result of the penetration of the surface of the fiber layer by the impervious coating, and as the folding operation is performed many of the brittle fibers penetrate the surface coating thereby exposing the absorbent inner fibrous material to the liquid or moisture of the contents of the container. In order to overcome this problem, according to one method, it has been found necessary to increase the thickness of the coating material to such a point where the brittle fibers at the surface of the fiber or paperboard layer are unable to penetrate the coating. Thus, in the case where polyethylene is used as the impervious layer or coating in spirally wound containers, such as disclosed in the Jensen et al. patent, a thickness of 0.0015 inches of polyethylene is required to be laminated onto paperboard of 0.0168 inches in order to prevent penetration of the extremity of the folds during the folding operation by the brittle surface fibers of the fiber layer.

Recognition of this problem has also led to the granting of several patents which disclose various methods of treating fold lines in laminated or coated paper or fiberboard containers in order to prevent leakage through the coating or barrier layer and into the main body layer of the structure at the folds. One such prior art patent is U.S. Pat. No. 3,374,715 to Koning, granted Mar. 26, 1968, which discloses pre-folding the treated fiberboard prior to curing the treatment impregnant. In other words, after pre-working the container blank at the fold area the impregnant, such as a stiffening resin, is then cured by heat thereby eliminating fractures formed in the barrier ply during the preworking operation. Another similar method is disclosed in U.S. Pat. No. 3,489,067, to I-Iallis, granted Jan. 13, 1970, which discloses pre-flexing the paperboard along the desired fold lines prior to impregnation with a solidification waterproofing agent to thereby seal any fractures produced in the paperboard at the fold lines. Yet another method is disclosed in U.S. Pat. No. 3,158,073, to Rumberger, granted Nov. 24, 1964, wherein the paperboard laminate is pre-folded at the fold line 180 and then folded to form a corner of the container, the cracks and ruptures beingtreated by reconsolidating as by remelting and fluxing of the thermoplastic adhesive bonding the barrier layer to the paperboard layer. However, it is to be noted that all of the abovementioned prior art processes disclose additional steps and the use of additional materials in order to rectify the defects in the fold lines which occur during the folding operation.

It is, therefore, an object of the present invention to provide an improved method of forming folds in coated fiber containers formed from a laminate comprised of a paper or fiberboard body layer having an impervious layer or coating laminated to a surface thereof which forms the interior of the container, the container is erected having folds therein which are formed by folding the laminate at fold lines so that only the coated surface is exposed at the folds and wherein penetration of the coating or barrier ply by the brittle surface fibers of the fiber or paperboard layer during the folding operation at the extremity of the folds is eliminated or substantially reduced.

The above object, as well as others which will hereinafter become apparent, is accomplished according to the present invention by providing a method of forming folds in a coated fiber container formed from a laminate comprised of an impervious coating pre-laminated to the surface of a paper or fiberboard layer and which forms the interior of the container, the method including inversely pre-folding or reverse folding the laminate so that the barrier ply or coating is folded upon itself whereby the surface fibers in the fiber or paperboard layer are weakened, distorted, and/or broken and also the coating material which has penetrated the fiber layer and that binds the fibers together is broken. Thus, when the principle folding operation is performed on the coated paper or fiberboard material so that only the impervious layer or coating is presented at the extremity of the folds, the coating at the extremity of the folds remains intact and free of punctures from the surface fibers of the fibrous layer underneath.

The method according to the present invention will be described and understood more readily when considered together with the accompanying drawing, in which: I

FIG. 1 is an enlarged cross-sectional view of a coated fiberboard material used in the production of a coated fiber container;

FIG. 2, is an enlarged cross-sectional view of the coated fiberboardof FIG. 1 having a bend or fold formed therein according the method of the prior art;

FIG. 3 is an enlarged cross-sectional view of the coated fiberboard of FIG. 1 showing a reverse fold therein according to the method of the present invention; and

FIG. 4 is an enlarged cross-sectional view of the coated fiberboard showing the fold therein resulting from the principle folding operation occuring subsequently to the folding operation of FIG. 3.

Referring now to the drawings wherein the method according to the present invention and the advantages derived therefrom are demonstrated, there is shown a laminate, generally designated 10, which can be used in the making of coated fiber containers such as of the folding type, lap seam containers, spirally wound containers, and convolute containers. The laminate is comprised of a fibrous material layer, generally designated 12, formed of kraft or chip board, having a coating 14 on one surface thereof which preferably forms the interior of the finished container. The coating 14 is impervious to liquid and gas and is for the purpose of providing a leakproof container adapted for the containing of liquids and other moisture yielding products. Preferably, coating 14 is formed from a suitable plastic material such as polyethylene. The coating 14 of polyethylene is preferably heat extruded onto the surface, generally designated 16, of the fibrous material layer 12. Due to the molten condition of the extruded polyethylene and the porosity of the fibrous material layer, the polyethylene penetrates the surface 16 of the fibrous material layer 12. This penetration of surface 16 by the coating material forms an intermediate layer, designated 18, wherein the fibers of the fibrous matewhich seeks to alleviate this problem, the laminate 10 is inversely pre-folded along fold line 20, as clearly seen in FIG. 3. It has been found that for best results the inverse fold, designated 30, should be a full 180 fold or bend, as shown. This inverse pre-folding causes the brittle fibers in the intermediate layer 18 at the center 28 of the inverse fold 30 to become weakened, distorted and broken and, in addition, the coating material binding the fibers together breaks into small segments 32, further reducing the brittleness and stiffness of the fibers in intermediate layer 18. As an added benefit, the

coating 14 at the center 28 of the inverse fold 30 is wrinkled during the inverse folding step which builds in an elongation into the plastic material by the compression to which it is subjected, thus during the principal folding operation the material is subjected to much less strain than it otherwise would be.

FIG. 4 depicts the final in the folding operation wherein a fold 24 is. formed along fold line 20. Since the stiff and brittle fibers 26 in intermediate layer 18 have been broken or weakened by the inverse folding operation, there is no penetration or piercing of the coating 14 at fold 24 by the fibers in the intermediate layer 18. Also, intermediate layer 18 at fold 24' is broken into relatively small segments 32, thereby serving to reduce the brittleness and stiffness of the intermediate layer thereat.

As a result of the instant method it has been possible to substantially reduce the thickness of the plastic coating, for example, where polyethylene is utilized as the barrier ply, a thickness of 0.0011 inches polyethylene laminated onto 0.0168 inches paperboard is sufficient.

It is understood that the foregoing general and detailed descriptions are explanatory of the present invention and are not to be interpreted as restrictive of the scope of the following claims.

rial layer 12 in the intermediate layer 18 are cohesively joined by means of the penetrating polyethylene.

Obviously, the fibers in the intermediate layer 18 are not free to bend as are the other fibers in the fibrous material layer 12 and, therefore, layer 18 is extremely stiff and brittle. Thus, when .the laminate 10 is folded at a fold line 20, as demonstrated in FIG. 2, which may be for the purpose of erecting a container, so that coating 14 is exposed at the extremity 22 of fold 24, some of the un-bending, stiff and brittle fibers, generally designated 26, in the intermediate layer 18 at the fold 24 penetrate and pierce the polyethylene coating 14 at the fold 24 during the folding operation. The moisture or liquid contained in the container enters through the punctures produced by the penetrating fibers 26 and is absorbed into the fibrous material layer 12 and by means of a wicking action the layer 12 becomes saturated.

According to the method of the present invention,

What is claimed is:

1. A method of making folds in a coated fiber container produced from a fiberboard layer having an impervious coating pre-laminated to a surface of the fiberboard layer which forms the interior of the container, the impervious coating penetrating the surface of the fiberboard layer thereby cohesively bonding the fibers in an intermediate layer at the surface of the fiberboard layer together, the method including inversely pre-folding the laminate thereby weakening, distorting, and breaking the surface fibers in the fiberboard layer which have been stiffened by the penetration of the. coating material, and folding said laminate along the same fold lines so that the fiberboard layer is folded upon itself and only the impervious coating is exposed at the extremity of the folds.

2. The method as defined in claim 1 wherein the laminate is inversely pre-folded through so that the impervious coating is folded upon itself.

3. The method as defined in claim 1 wherein said impervious coating is formed from a plastic material.

4. The method as defined in claim 3 wherein said plastic material coating is polyethylene extruded onto the surface of said fiberboard layer. 

1. A METHOD OF MAKING FOLDS IN A COATED FIBER CONTAINER PRODUCED FROM A FIBERBOARD LAYER HAVING AN IMPERVIOUS COATING PRE-LAMINATED TO A SURFACE OF THE FIBERBOARD LAYER WHICH FORMS THE INTERIOR OF THE CONTAINER, THE IMPERVIOUS COATING PENETRATING THE SURFACE OF THE FIBERBOARD LAYER THEREBY COHESIVELY BONDING THE FIBERS IN AN ITERMEDIATE LAYER AT THE SURFACE OF THE FIBERBOARD LAYER TOGERHER, THE METHOD INCLUDING INVERSELY PRE-FOLDING THE LAMINATE THEREBY WEAKENING, DISTORTING, AND BREAKING THE SURFACE FIBERS IN THE FIBERBOARD LAYER WHICH HAVE BEEN STIFFENED BY THE PENETRATION OF THE COATING
 2. The method as defined in claim 1 wherein the laminate is inversely pre-folded through 180* so that the impervious coating is folded upon itself.
 3. The method as defined in claim 1 wherein said impervious coating is formed from a plastic material.
 4. The method as defined in claim 3 wherein said plastic material coating is polyethylene extruded onto the surface of said fiberboard layer. 